Solid propellant technology has been advanced considerably during recent years because of the R & D dollars that have been expended to fund many programs devoted to the many specialized areas of solid propellant technology. For example, the burning rates of propellants have been increased by use of improved burning rate catalysts, by the use of recently developed energetic plasticizer compounds, and by the use of small particle size oxidizers.
Many problems have arisen during the development and use of small particle size oxidizers. The manufacturing of small particle size oxidizers has been difficult to accomplish, particularly, in the particle size range of 0.25 to 5.0 micrometers. The reduction in particle size of the oxidizer, ammonium perchlorate (AP), has created special problems relating to processing of propellants, particularly, the mixing of the propellant and the casting of the propellant. The major problem in mixing and casting propellants using hydroxy-terminated polybutadiene and very small particle size AP (less than 20 micrometers) relates to pot-life. Pot-life is the time during which the propellant mix retains its proper fluid properties to permit mixing and casting.
It has been determined that pot-life can be extended with the use of AP that is coated with particular aziridine compounds. Coating of very small particle size AP has been difficult to accomplish because of the tendency of the fine grind AP to stick together rather than remain separated in individual particles. The present invention is concerned with fine grind AP that is coated with an aziridine compound.
Therefore, an object of this invention is to provide a method for preparing small particle size coated ammonium perchlorate.
Another object of this invention is to provide a method for grinding and coating ammonium perchlorate with an aziridine compound.
A further object of this invention is to provide an ultrafine ammonium perchlorate that is coated with an aziridine compound and that has particle sizes ranging from about 0.25 to about 5.0 micrometers, weight median diameters, and that has specific surface areas from about 1.3 to about 13.0 m.sup.2 /g (square meters per gram).